Beat egg whites with an electric mixer. Just before peaks form, slowly add one-fourth cup sugar with mixer running. Set aside in a cool place.

Beat whipped topping until peaks form. With a spatula, gently fold it into the egg whites.

Using a food processor fitted with the S blade, crush a half cup of pistachios with remaining half cup sugar until very well crushed.

Add remaining half cup pistachios and pulse until chopped into chunks.

Fold into egg white-whipped cream mixture.

Line two small loaf pans with plastic wrap, leaving a little hanging over the edges for easy removal. Alternatively, you can use silicone loaf pans.

Pour mixture into prepared pans and freeze overnight. Immediately before serving, invert the semifreddo onto a platter and garnish with crushed pistachio, meringues, and fruit.